Radio receiver



w. RUNGE ET AL Jgly11,1939.

RADIO RECEIVER 'Filed Dec. 17, 1935 r. M c

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Patented July 11, 1939 JNPE RADIO RECEIVER Wilhelm Runge and Alfred Kunz-fe, Berlin, Germany, assignors to Telefunken Gesellschaft fr Drahtlose 'lielegraphie 1n. b. H., Berlin, Germany, -a corporation of Germany Application December 17, 1935, Serial No. 54,807 In Germany December 20, 1934 4 Claims.

'I'his invention relates toan improved arrangement of apparatus for receiving oscillations. The present invention is an improvement over a patent application Serial No. 31,814, filed July 17, 1935, which application has since become abandoned.

The parent application relates to a receiver arrangement with a sharp threshold of response for increasing the proportion between two or a greater number of amplitudes of different values in favor of the greatest amplitude. The threshold of response of the receiver arrangement is thereby always so placed dependent upon the respective amplitude, that it lies directly below the greatest amplitude. In accordance with the parent application this receiver shall be preferably employed for rendering more distinct the side identifications of radio beacons.

Arrangements in accordance with the parent application are primarily suited for enlarging the amplitudinal proportion between two or a greater number of signals cf different amplitudes successively transmitted.

The present invention is concerned with receivers destined for indicating among a number of simultaneously appearing signals of different frequencies only the signals of that frequency which presents the absolutely greatest amplitude.

In accordance with the invention, at the reception of oscillations modulated by different frequencies, an apparatus is employed in which the low frequency output of one or several receivers is collected and applied to an arrangement of multi-mesh or infra-pass ltors placed in parallel which separate the individual modulation frequencies. Now there is provided for each modulation Vfrequency present either an apparatus for increasing the steepness according to the parent application Serial No. 31,814 whereby according to the invention the desired mutual dependence of the arrangements is obtained in that the capacitive and resistive combinations of all apparatus for increasing the steepness are placed in parallel, or only a single apparatus for inv creasing the steepness according to application Serial No. 31,314 is used and the individual modulation frequencies are applied to the steepening apparatus in succession at definite sequence of time intervals by means of a switch. The term steepening apparatus as it appears throughout this application shall mean any arrangement which is suitable for emphasizing the larger of two or several signals (impulses) and at the same time for suppressing the smaller one. U. S. Pat. #2,026,361 discloses such an arrangement. The purpose of these arrangements is to increase the amplitude ratio so that with initially small differences it may be clearly recognized, after passage through the arrangement, which of the individual amplitudes is the absolutely maximum (Cl. Z50- 20) one, In accordance with the teachings of said Patent 2,026,361 it is found practical in cases of this kind to produce a differentiation between the gain ratios of the amplifier applicable to relatively strong and weak signals respectively. The means for accomplishing this comprise a suitable self-biasing resistor in the grid circuit of the amplifier` and a suitable capacitor in shunt with said resistor. When using such an arrangement if two different frequencies are simultaneously received and the signals at one frequency predominate in amplitude over signals of the other frequency, then the sum total of the self-biasing effect is such as to render the grid of the amplifier tube at least as negative as would result from the reception of the stronger signal alone so that only the peaks of the stronger signal become effective and the peaks of the lesser signal do not rise above the cut-olf point of the tube characteristic. A special indicator is provided for each frequency. The amplitude of the signal of absolute greatest value will then be clearly indicated at one of the indicators such as for instance a pointer instrument. In the first mentioned embodiment the signals appearing simultaneously in certain periods of time are retained in their relation. In the second embodiment due to the common steepening apparatus the simultaneous appearance of signals in time periods is transformed by the switch intoa subsequent appearance as regards time.

In practice, it is often necessary to identify and indicate separately several routes not always necessarily starting from the same point. To this end there are employed at the transmitter side several directional antennae, for instance, preferably operating on the same wave length, and radiating at definite angles to each other. Hereby, each high frequency radiation will be modulated by another tone frequency but always at constant amplitude. The lines of equal eld intensity of two adjacent radiations are utilized each for identification of a border of a sector, or of a certain travel route.

The receiver apparatus according to the invention may as is obvious, also be used for identifying the relative direction of travel of a ship for instance, where the transmitter of the ship radiates, in several sectors stationary in relation to the ship, preferably directed electro-magnetic radiations distinguish-ed by different modulations of audio-frequency for instance. The sectors, as regards their opening angles and orientation with respect to the ship, correspond to the customary guiding colors for ships, namely green, white, red. The line of equalaudio-frequency amplitudesv 0f adjacent radiations serves for identifying the border of the sector.

The purpose of the receiver apparatus according to the invention is to indicate in an unequivocal manner and with the sharpest definition the sector received or in which the craft moves.

The functioning of the receiver apparatus according to the invention, will now be elucidated by Figures 1 and 2 shown as examples.

In an apparatus according to Figure 1, separate steepening apparatus V1, V2 and V3 are provided one for each modulation frequency. The audio-frequency output energies f1, f2, f3 are collected at the terminals A, B of one receiver or of several receivers in case of different carrier waves, and are applied to aV filter chain arrangement. At each of the multi-mesh filters L1, L2, L3 suitable pointer instruments T1, T2 and T3 are placed across steepening apparatus V1, V2, V3 and detectors G1, G2, G3

The position of the receiver with respect to the transmitter can be ascertained from the combination of the indications of all instruments.

Since, in accordance with the invention, the audio-frequency signal which possesses the greatest absolute amplitude is to predominate over other signals, a common condenser-resistance-combination is provided and so connected that it is simultaneously included inthe grid circuits of all V1, V2 and V3 apparatus operating in parallel. In this way all steepening apparatus receive the same negative grid bias, always determined by the greatest of the simultaneously present audio-frequency amplitudes. In orderY to avoid various audio-frequencies from entering nearby steepening apparatus across the capacitive and resistive combination, it is ad-Y visable to tune the input and output circuits of the V1, V2, and V3 apparatus to the frequency to be transmitted and eventually to provide blocking circuits for the remaining frequencies.

In an embodiment according to Figure 2, a common steepening apparatus V is provided placed successively by means of a commutator Y type of rotatable switch U1 at the multi-mesh or infra-pass filter units L1, L2, L3 The output circuit of the steepening apparatus is connected to a second switch U2 across a detector G, the said switch being actuated simultaneously with the switch U1. As a result of this measure there will be connected in successive time periods the filter L1 to the indicating instrument T1 across stages V and G and filter L2 to instrument T2 etc.

The simultaneous operation of theswitchesV U1 and U2 may be rotated by hand, or by means of a progressive switching movement with self L interrupter, by means of a motor or clock movement, etc. The speed of switching such as for instance the number of revolutions per second of a contact switch according to Figure 2a will preferably be chosen greater than the time constant of the capacitive and resistive combination in the steepening apparatus.

In establishing the speed of switching, consideration is to be given to the moment of inertia and the damping of. the measuring systems in the indicating instruments in order to prevent false indication. Preferably, the speed of switching should be so adapted to the inertia and the damping of the measuring system that there will be obtained an approximately gradual indication.

The idea of the present invention is not limited to the stated examples of embodiments. An acoustic indication by means of a telephone or an optical indication by means of a Frahms or vibratory reed may be employed with equally favorable result.

We claim:

l. Apparatus for receiving oscillations modulated by a plurality of simultaneously occurring signal frequencies comprising input and output portions, filtering means for separating the various signal frequencies, said means comprising a separate filter for each frequency having capacitive and resistive reactance connected to said input portion, separate amplifying means for each filtering means comprising a thermionic device having an anode, grid and cathode to increase the amplitude ratio between the smaller and the larger ofY said impulses, said amplifying means being connected to each of said filters, a common condenser and resistance connected to the grid circuits of said amplifying means, and indicating apparatus connected to the output portion of said receiving means. 1

2. Apparatus for receiving oscillations modulated by a plurality of simultaneously occurring signal frequencies comprising input and output portions, filtering means for separating the various signal frequencies, said means comprising a separate filter for each frequency having capacitive and resistive reactance connected to said input portion, separate amplifying means for each filtering means comprising an electron discharge device having at least an anode, grid and cathode, the grid circuit of which is connected in parallel with said capacitive and resistive reactance to increase the amplitude ratio between the smaller and-the larger of said signal impulses, said amplifying means being connected to each of said filters, a common condenser and resistance connected to the grid circuits of all of said amplifying means, and indicating apparatus connected to the output portion of said receiving means.

3. Apparatus according to claim 1 characterized in that the various signal frequencies are supplied in succession across a rotatable switch to a common amplifying apparatus for steepening the amplitude after passing through a subsequent detector, and a second rotatable lswitch connected to said detector which is connected to aI separate indicating instrument assigned to the signal frequency to be switched.

4. Apparatus for causing onekind of a plurality of differently characterized signal impulses to produce a dominant indication while suppressing the effects of other signals simultaneously received, comprising a radio receiver having a demodulator, a plurality of signal-frequency filters connected in parallel to the output side of said de-modulator, a gain-controlled amplifier, means including a time constant circuit having a resistor in shunt with a capacitor for increasing the differentiation between the gain ratios of said amplifier applicable to relatively strong and weak signals respectively an indicator having a plurality of indicating devices each connectible to a respective one of said filters, and constantly rotatable switching means connected between said filters and said amplifier, also between said amplifier and said indicator for directing said signals into appropriate ones of the indicating devices in accordance with their frequencies.

WILHELM RUNGE. ALFRED KUNZE. 

